Two-hand control for power actuated machines



April 1s, 1944. E AWS 2,346,829

TV10 HAND CONTROL POR POWER MITUATBD MACHINES Filed Juno 6. 1941 4 Sheets-Shut 1 si luumv- /f a E N INVENTOR ERNEST DAVIS www ATICRNEYS.

April 18, 1944. E. DAVIS 2,346,829

TWO HAND CONTROL FCR POWER AGTUATED MACHINES Filed June 6. 1941 4 Sheets-Sheet 2 NVENTOR ATTORNEYS.

E. DAVIS April 18, 1944.

TWO HAND CONTROL FOR POWER ACTUATED MACHINES Filed June 6, 1941 4 Sheets-Sheet 3 FIG.6

ff 'A f A f 1... 4Hillilllllnlll INVENTOR ERNE ST DAVIS Y mv/w ATTORNEYS April 18, 1944. E. DAVIS 2,346,829

Two HAND con'rRoL Fon Powrsn Ac'rUA'xE MACHINES Filed June 6. 1941 4 Sheets-Sheet 4 |NVENTOR- BY ERNEST DAVIS w ATTORNEYS.

Patented Apr. 18, 1944 TUVO-HAND CONTROL FOR POWER ACTUATED MACHINES Ernest Davis, Syracuse, N. Y., Vaaslgnor to The Prosperity Company, Inc., Syracuse, N. Y., a

corporation of New York Application June 6, 1941, Serial No. 396.959

Claims.

This invention relates to two hand controls for power actuated machines having an operatlng movement, which is dangerous to the opera.- tor, as a machine having an opening and closing movement; and has for its object a two hand control lncludlnar a pressure tank, a pair of manually operable control valves, either one of which is of insufficient size er capacity to conduct suiilcient pressure or worklna fluid from the tank to effect the operation of the machine. so that the instantaneous or simultaneous operation of both manual valves is required to effect. the operation, and means in the control valve system lor supplying sufficient pressure through the control valve when both are simultaneously operated io eliect the operation of the machine, and also a disabling or bleedina means which reduces the pressure in the tank when only one manual valve is operated to below the required pressure for operating the machine when the other manual control is operated, so that if the valves are alternately operated and not simultaneously operated, there is not sufficient pressure in the control system to eiect the operation of the machine.

It further has for its obiect an arrangement of the bleecler or disabling means in such a manner that the pressure is maintained to operate the machine only lone enough to permit the machine to operate lf the operator holds both manual conti-ds in operated position. after the machine closes. or in machines as punch presses, in which each operation, thc opening movement immediately follows the closing movement, repeated operations can not take place upon one operation of the two manuals.

It further has for its object a master control valve and locking means therefor.

Other objects appear throughout the spcclication.

The invention is illustrated as applied to a garment and laundry press in which a press head moves inwardly and out of coactlon with a press table or buck.

The invention consists in the novel features and in the col'nbinafiorrv and constructions hereinafter oet forth and claimed.

In describing this invention. reference is had 1o the accompanyin': characters designate corresponding parts in all the views.

Figure l is a perspective view ol' n laundry press embodying this invcnflon.

Figure i. is on enlarged sectional View nl' the master conrol valve.

Figure 3 is a section on rnc 3-3. Future 2. Figure 4 is a diagrammatic view. partly in section, illustrating the control system and power system for the cylinder and piston motor drawincs in which like i of the press, the various valves and the cylinder andpiston motor being shown in longitudinal section.

Figures 5 and 6 are respectively a side eleva tion and an end view of a modified form of the master control valve.

Figure 7 is an elevation, partly in section. of

`a second modified form of the control valve.

Figure 8 ls a diagrammatic view similar to Figure 4 ol a modied form of the control system.

Figure 9 is a perspective view of a modified form of the manuals for operating the manually operable valve and the arrangement of manuals on the table of the pressing machine.

The pressing machine to which this control system is applied. as here shown, comprises a head I movable toward and from a buck 2 sult ably mounted on a frame 3 of the machine above the table The head l ls carried by a head carrying lever 5 pivoted at 6 to an arm 1 rising from the frame 3 in the rear of the buck 2. It is actuated by a cylinder and piston motor including s. cylinder 8 suitably pivoted Within the frame to have an oscillating movement, and a single acting piston i0 in the cylinder, the rod il of which is connected at I3 to a lever I2 forming part of a motion transmitting means between the piston rod and the head carrying lever 5. In so far as this invention is concerned. the construction of the machine forms no part of this invention. as the inven tion relates to two hand control for controllingf the flow of a Working or pressure fluid to the cylinder B.

The two hand control includes a self-closing. normally-closed master valve for controlling the ow of working fluid from a main pressure line to the motor, a pair of self-closing, normallyclosed manually operable control valves connected to pressure operated means, which open the master valve. each manual control being of lnsulcient size or capacity to conduct suiiicieut pressure' fluid to operate the pressure operated means in the master control valve, each manual control valve being a combined intake and cxhaust with thc intake normally closed and the. exhaust open, a pressure tank also connected in the main line and to the manually operated control valves and being of sumclent capacity only to supply pressure fluid through the manually operated control valves to the pressure operated means of the master valve for one openina operation only of the master control valve, upon simultaneous or instantaneous operation of both controls, together with disabling means for releasing thc pressure iluid to the pressure operated means of the master valve at a predetermined rate when either or both control valves are operated, so that instantaneous or simultaneous operation oi both control valves is required to operate the master valve: and further so that the pressure is released. permitting the master valve to close after a predetermined time period when both manual valves are operated simultaneously, unless locking means hereinafter set forth are employed. The valve arrangement is suoli that the absence of locking means repeated operation is prevented upon one simultaneous operation oi the manual valves.

2l designates the master control valve. this lncluding a casing 22 having a self-closing, normally-closed, intake valve head 2l therein, a pressure chamber 24 having a piston 2l therein connected by a stem 2G to the intake valve head Il. so that the two act as a unit. The casing is also, in this embodiment of the invention, provided with a second pressure chamber 21 therein. in which works a piston 28 connected by a stem 29 to the piston 25. The control valve 2| is also provided with a port 30 which communicates with a conduit Il leading to the intake end of the cylinder 8 and controlled by the intake valve head 23. The intake valve head 23 is acted upon by a returning spring 32 to close the same. The portion oi the casing 22 of the master valve. which is controlled by the valve head 23, is connected by a pipe 33 to the main line Il ot a pressure supply pipe which is connected to a suitable source of compressed air. 36 and I6 designate respectively the manually operable two hand control valves, each of which includes a casing 31, a combined intake and exhaust valve therein including an intake head IB, a normally-open exhaust head lil connected by a stem Iii sothat they act in unison, the unit being normally held with the intake closed and the exhaust open by the spring 4i. The exhaust valve head is shown as formed with a stem 42 extending outside of the valve casing, where it coacts with a manual 43. When only one valve I or I6 is opened, the air will ilow out past the open exhaust head of thc other valve through port 38".

The manuals shown in Figures l and 4 are depressible plates normally tlush with the surface of the table I, they being here shown as hinged at u and depressible against the action oi returning springs l5. When depressed, they strike the stems 42 and operate the control valves 35, 38 against the action of the returning springs 4I.

46 designates a pressure tank connected in the main supply line 24 in multiple with the pipe 23 and also connected preferably in multiple with the valve casings o! the manual valves 25, 3B f through pipes i8, I9.

5D designates a throttle valve located in theA iront edge of the table. D is a valve-controlled drain pipe for the tank. Also, the tank and throttle valves are preferably enclosed within a suitable housing 5J. The casings 31 of the manually operable valve I5, 86 have outlet ports communicating with a pipe 54 which communicates with the pressure chamber 24 oi.' the master valve 2|. When the valves I5. 3B are operated simultaneously by depressing the manuals 4l, the lntake valve heads 38 thereof are opened against the action of the springs 4i and the exhaust valve heads 39 closed. so that air passes from the tank 4B through the pipes 48, 48 to the intake ends of the valve casings Il past the open intake valve heads and out through the pipe 64 to the pressure chamber 24 of the master control valve 2l, thus actuating the piston 25 to open the valve head 23, so that air will pass from the mainline 34 through the pipe 4I to the valve casing of the master valve, past the open intake valve head 23 out through the port 80 and conduit Ii to the cylinder l and actuate the piston i0 on its power stroke to close the machine. If but one manual valve 3l is operated, the pressure passing through the pipe It is insumcient to operate the piston 25 in the master control and also passes out through the exhaust port 38 of the other valve.

The disabling or bleeder means consists o! a bleeder passage 55 through the partition between the pressure chambers 24 and 21 o! the master control valve, this passage having an adjustable needle valve 58 therein. The throttle valve 5i is similar in construction to the valve IB.

The chamber 21 oi' the master control is formed with exhaust passages l1 which open to the outer air. Thus, when but one manually operated valvp 31 is opened. the pressure fluid bleeds out through the passage 55 and to the outer air through the passage I1 and also out through the exhaust passage 38* oi the other manually operated valve, so that if the control valves 35. le are operated alternately and not simultaneously. there will not be sunlcient pressure in the cham ber 3l of the master valve to actuate the piston 25. The press is opened by releasing the pressure fluid in the cylinder Il through the master control valve, as will be hereinafter described.

'I'he purpose of the bleeder passage Il is to prevent sufl'icient pressure building up in the chamber 24 of the master valve to actuate the piston 25, and hence open the master valve 23, when one of the manual valves 31 is held operated by one hand and the other is in normal position, and subsequently the operator inadvertently operates the other valve, as by inadvertently leaning against the manual thereof. so that pressure gradually builds up in the tank through the valve 50 to a point where suilleient pressure would otherwise build up in the chamber 2l of the master valve to actuate the piston 25. This operation is possible and has occurred. although it is `not a common occurrence. for the operator to operate one manual valve 36 or I8 with one hand and to continue in laying the garment on the pressing element 2 with the other hand, and while so doing, move her body around so as to inadvertently operate the other manual valve. The inadvertent operation causes the pressure to build up to operating pressure in the tank 4B through the valve lill, and hence the press closes while the operator is still arranging the lay with one hand. By reason of the bleeder il. the pressure fluid entering the chamber 2l bleeds out through the passage 5l as fast as it feeds into the tank 4 IB through the valve Bil.

In a pressing machine, such as a garment or laundry press. the machine remains closed and is opened at the will oi' the operator by operating the release valve or the release valve may be automatically opened by a timer after a pre determined period. In the machine here shown, the machine ls opened by operating manually operated release valve which releases locking means for holding the master valve in its opassunse 3 erated position. The means here shown consists or a connection operated by the closing movement or the press. This connection is here shown as a pipo 58 leading from a port It in the side and the piston iii passes the port t0. air under pressure from the cylinder passes from vthe pipe 5I to the chamber 21 of the vmaster valve on the pressure side thereof and thus holds the intake valve head 23 in its open position. The valve head 23 is returned toits normal closed position upon the operation ol a release valve previously referred to, which operates to exhaust the air from the pressure side of the chamber 21 oi' the master valve.

62 designates the release valve, this including a casing 03 and a self-closing. normally-closed exhaust valve 84 therein, it being closed by s.`

`spring E5. The end of the stem of the valve is arranged to bf: depressed by a manual 6U similar to the manuals 43. The valve casing M is connected to the chamber 21 by a pipe l1. Upon the able outlets B9 which with the passage 51 prethe main supply to the tank and around the throttle valve B0. 14 designates the valve casing having a normally-closed intake valve Il therein. the casing being connected on the inlet side of the valve head 1l to the main line Il by a conduit 'I6 and from the opposite side ol the valve head 1l to the tank 46 by a pipe 11. The valve head 1t is closed and normally held closed by a spring 1l. It is opened by a pressure operated motor consisting of a diaphragm chamber 'I9 having a diaphragm 8U therein pressing against the head oi' a plunger li which thrusts against a second web or diaphragm 82 which in turn thrusts against the head Il on the stem Il of the valve head 1l. The space between the two diaphragme is vented to the outer air through passages B5. The pressure side of the diaphragm chamber 19 is connected by a pipe I6 to the pipe 54 from the two hand control valves 35, 28. When both two hand controls are operated, the pressure iiuid enters the diaphragm chamber at the same time it enters the chamber 24 of the master control valve and actuates the diaphragm all therein to open the intake valve to permit air to pass unthrottled from the main line 34 to the tank 48 around the throttle valve 50.

The spring 1l is o! sufllcient strength to hold the valve 15 closed against opening by the dlaphragm It under the air pressure that would be vent the pistons 25, 2B from becoming air-bound.

In Figure 2. the master control valve is shown` -I in detail. and the piston is a unit with a valve seat 23* connected to the normally-closed intake valve head 23. `The head 23I is a normally open exhaust valve. The heads 23, 23* constitute a. two-wav or a combined intake and exhaust valve. The exhaust valve head 23- seats on the valve seat 1| when it has been operated by the two hand control operation to open the intake valve head 23. so that when this intake valve head 23 is open. the air pressure can not pass into the chamber 26, and when the release rvalve is operated. the air can exhaust from the cylinder 8 through the pipe 3i into the chamber 2l and out through the passages E! and also the air blending through the passage into the chamber 21 can bleed out through the passage 51 insieod oi being trapped. These exhaust passages E9. 1E open into a passage which constitutes murders 12. 13 of any suitable construction.

ln a machine where the head or movable part has o continuous closing and opening movement, or does not remain closed. or where the opening movement follows immediately the closing movement, the automatic locking means controlled my the movement of the machine may be omitted, in which case, owing to the pressure tank 46 and the two hand control system. repeated operations of the press can not take place upon one operation of both manuals, because of the predetermined time element required to build up suiilcient pressure in the tank IB to effect the operation of the master control when both manuals are operated.

ln Figure 8 is shown o. construction by which the pressure in the tank required to operate the master control valve when two manuals are operated simultaneously may be built up quickly for last successive but simultaneous operation of the pair of manuals. This feature consists of a normally-closed valve in the pipe line from passed bythe operation of one manual only. The operation of both manuals is required to conduct suilicient pressure against the diaphragm B0 to overcome the spring 18.

The construction shown in Figure 8 is provided with release means similar to that shown in Figure 4, but the locking and the release means may be omitted. One way of dispensing with them is by locating a cut oil' valve 01 in the pipe 59 leading from the port in the side of the cylinder to the pressure side o! the piston 2li in the chamber 21 of the master control. In Figure 8. the manuals for operating the valves are shown as slightly different from those shown in Figure s. In Figure 8. instead of being deprcssible plates or panels in the table, they are elongated strips or plungers 88 sliding in slots formed in the table against the action of returning springs I9.

In Figure 7. the master control valve head is shown as operated by diaphragme instead ol cyllnders and pistons. and the bloeder or disablins means located to bleed the air from between two diaphragrns. 210 designates the master control valve: 9U the casing thereof: 9i the intake valve head correspondingv to the head 23 (Figure 4l: 92 the spring for closing the valve 9|; 83 the main line intake pipe; and $4 the out-let to the cylinder l. 95 designates a plunger connected by a stem 56 to the valve head 9|. so that, they act as a unit. This plunger. when operated. sont; against a seat li. 91 is a pipe connected to the two hand control and corresponding to the pipe 54 (Figure 4l. $8 is a diaphragm located in the diaphragm chamber at one end of the Casini:

95. the diaphragm thrusting against the head on Y the. plunger 95. 99 is the second diaphragm `spaced from the diaphragm 98 and separatist:

side oi the cylinder l. In operation, when both the two hand controls are operated simultaneougly su-tilcient air pressure passes through the pipe 91 past the disabling valve into the chamber between the diaphragms to actuate the Piungers 95, and hence. open the intake valve head 0| to the intake of air from the main line, so that air passes past the valve head 9| and out through the plpe Il to the cylinder l to actuate the piston therein. When the piston passes the port in the side of the cylinder, air passes through the pipe |63 from the diaphragm chamber IBI actuating the diaphragm 99 therein to follow up the diaphragm 9| and hold the plunger 0l in its operated position, and hence hold the valve head 9| open to the inlet of air from the main line to the cylinder l. Upon the operation of the release manual, the air is exhausted from the diaphragm chamber lill. the same as it is exhausted from the chamber 21 in the construction shown ln Figure 4. When the air is thus exhausted from the diaphragm chamber IUI. the intake valve head 9| closes under the impetus of the spring 92. Also, the plunger 85 is moved into the position shown in Figure '7, so that the air can exhaust from the cylinc-ier back through the pipe 94 past the valve seat 98 into the plunger chamber 95 and out through the exhaust passage |04.

In Figures and 6. the cylinders and pistons for opening the master control valve and locking it closed are shown as arranged parallel with the master control valve instead ot in alinement therewith, as in Figures 2 and 7.

In Figures 5 and 6, |85 designates a body in which the valve head |06, corresponding to the valve head 23, operates, this having a stem lill connected to the intake valve 23 oi the master control (Figure 2) and coasting with the seat on the body 30 (Figure 2). the same as the valve 23* coacts with its seat. The valve |08 is provided with a stem |08 extending outside oi' the body |05. |09 and H0 are cylinders mounted parallel to each other at one side or above the body IUS and supported thereon. as by a bracket iiil pistons corresponding to the pistons 25 and 28 operating in the cylinders |09 and lill, respectively, the rods I|2 and ||3 of these pistons exlending to the outside of the cylinders, the cylinder |99 being connected to a pipe corresponding to the pipe il (Figure 4) which conducts the pressure from the manual control valves and the cylinder H0 being connected to a port in the side of the power cylinder 8 by a pipe corresponding to the pipe 59 (Figure 4). The motion of the pistons il! and H3 is transferred to the rod lil through a Y-shaped lever I Il having a hub or mounted on a pivot ||5 extending through ears ||6 on the bracket I||. The arms of the Y formation coact respectively with the ends of the piston rods H2. H3 and the leg of the Y formation coasts with the end of the valve rod lill. The body |95 is provided with exhaust passages constituting a muffler IiI corresponding to the muilier 69 and of the same general construction, the muiiier having outlet perforations I Il opening into the outer air. In operation, when the manuals are simultaneously operated, alzenters the cylinder |Il9, actuates the piston and its rod III. rocking the lever H4 causing the leg of the Y formation to thrust on the end o1' the rod |08 and move the valve |06 on its seat corresponding to the seat 'Iil (Figure 2l and through the stem |81 open the intake 23 oi the master control, so that air passes by the intake 23 through the passage ol the body 30 into the power cylinder 8. When the piston in the power cylinder 8 passes the port I0, air passes through the pipe to the cylinder H0. actuates the piston therein to bring the end of its rod H3 against the other arm of the Y formation of the lever Il# and thus hold the lever Iii. and hence the valve IIIB and the intake valve Il of the master control in the position into which it has been operated by the piston in the cylinder 8. upon the proper operation of the manually operated valves It, at. The cylinder lit is also connected to a release valve, as I2, through a pipe corresponding to the pipe Il, so that upon operation of the release valve, the air from the cylinder lili is exhausted, permitting the intake valve 2l to close and the valve lili to open, and hence the air exhaust from the power cylinder l out through the muilier ill in a manner similar to the construction shown in Figure 2.

In all constructions. there is only suiiicient air in the pressure tank 66 to eiect the operation oi the piston l! or the diaphragm 9B or the piston in the cylinder |09 upon the simultaneous operation of both manually operated valves 3B, 38 and the operation oi.' one valve ahead of the other results in the lowering o! the pressure in the tank 46 to such an extent thatthere is not suillcient pressure to operate the master control valve upon alternate operation of the manually Operated valves. Also, upon the proper simultaneous operation of the two liand control valves 36, It, the pressure although sutliclent to operate the master control 4valve immediately bleeds out through the passage El, so that the operator must hold both valves depressed for a predetermined period. Ihis period in the machine here illustrated is long enough i'or the head to come down close to the buck 2 or long enough for the piston ||I to uncover the port B0, which controls the ilow of air through the locking cylinder 21 or the diaphragm chamber (Figure 'Il or the cylinder (Figures 5 and 6).

In machines in which the opening and closing movement is continuous without the machine remaining closed and in which means for locking the machine closed is dispensed with, the b1eeding oi the air through the bleeder valve l5 prevents successive operations upon one simultaneous operation oi both manually operated valves 3l, IB. In machines with such an operation, it may be necessary to build up the pressure in the tank 4B faster than in machines which are held closed for a period ot time, instead of being instantly opened. In such machines. the tank 46 may be built up to the required pressure in a shorter time by eliminating the throttle valve |I|| or shunting around the throttle valve B0, as seen in Figure B, by means oi the pipe 11. The time element in filling the tank 46 to the required pressure is suillcient to require the repeated operations of the manually operated valves 3l, 36.

What I claim is:

1. A two hand control for power actuated machines having a pressure operated motor, including a self-closing, normally-closed master valve for controlling the iiow o! working iiuid to the motor and pressure operated means for operating it, a main working duid supply line connected to said master valve and normally closed thereby. manually-operable. sell-returnable control valves of the combined intake and exhaust type normally arranged with their intakes closed and exhausts open, a tank connected in the main line. and a throttle valve located to time the flow o! pressure iiuid from the main line to the tank. and the building up of pressure in the tank to a predetermined pressure, the tank being connected in multiple with the control valves and the control valves being connected in multiple with the pressure operated means of the master valve, the tank being ol sufllcient capacity only to supply pressure to the pressure operated means of the master valve for one opening operation only oi' the master valve, all whereby upon operating only of one control valve, the pressure fluid exhausts through the other control valve, and the pressure ol the tank drops below a predetermined and sufcient pressure to operate the pressure operated means of the master valve and the operation or both control valves substantially in unison is required to operate the master valve. and bleedei' means ior gradually releasing the pressure in the pressure operated means oi the master valve.

2. A two hand control for power actuated machines having a pressure operated motor includ ing a sell-closing, normally-closed, master valve for controlling the flow o! working fluid to the motor and pressure operated means for opening it, a main working fluid supply line connected to said master valve and normally closed thereby, a pair of manually operable control valves cach having an inlet port, an exhaust port, and an outlet port, said valvesnormally arranged with their inlet ports closed and their outlet ports communicating to atmosphere through said exhaust ports and operable to open their inlet ports in communication with the outlet ports and to close their exhaust ports, a tank connected in the main line through a throttle valve arranged to time the now of fluid from the main line to said tank and the building up of main line pressure in the tank, the inlet port of each valve beine connected to the tank and the outlet ports ol' said valves being connected in multiple with the pressure operated means of the master valve, the tank being of suiicient capacity to supply fluid to the pressure operated means of the master valve sunicient only for one opening operation of the master valve, all whereby upon operating only one of the control valves the working fluid exhausts from the tank through the other control valve leaving an insuii'lcient supply o said iiuid to operate the pressure operated means of the master valve upon suscquent operation oi Said other control valve. and the operation of both. control valves substantially simultaneously is re quired to operate the master valve, and bleeder means for gradually releasing the pressure in the pressure operated means of the master valve, said bleeder means being adjusted to permit a now o fluid at least equal to the flow oi lluid through said throttle valve.

3. A two hand control for ,power actuated machines having a pressure operated motor including a self-closing, normally-closed. master valve for controlling the flow oi working uid to the motor and pressure operating means for opening it. a main working iiuid supply line connected to the pressure operated motor through said master valve and normally closed thereby, a plurality of manually operable. sell-returnable control valves. the inlet ports of said valves being connected in multiple to said supply line, and the outlet ports or said valves being connected in multiple to the pressure operated means o! the master valve. bleeder means operable to gradually release the pressure in the pressure operated means oi the master valve, said control valves. when operated substantially simultaneously, permitting suillcient fluid to now to said pressure operated means to eiIect opening of the master valve. and said bleeder means being operable to bleed oi! sumcient fluid upon the operation of any one of said control valves to prevent suilicient operating pressure in said operating means oi the master valve.

4. A two hand control i'or power actuated machines having a pressure operated motor including a self-closing, normally-closed, master valve for controlling the ilow o working fluid to the motor and pressure operating means for opening it, a main working iiuid supply line connected to the pressure operated motor through said master valve and normally closed thereby, a plurality o! manually operable, sell-returnable control valves, the inlet ports of said valves being connected in multiple to said supply line, and the outlet ports ci said valves being connected in multiple to the pressure operated means of the master valve. bleeder means operable to gradually release the pressure in the pressure operated means oi the master valve, said control valves. when operated substantially simultaneously. permitting sufilclent :luid to iiow to said pressure operated means to cl'iect openingo the master valve.and said bleeder means being operable to bleed off sumcient uid upon the operation of any one o! said control valves to prevent sufilcient operating pressure in said operating means of the master valve. and means operable upon such simultaneous operation oi' said control valves to instantly replenish the upply oi fluid in the tank for a successive operao. A two hand control for power actuated machines having a pressure operated motor including a sell-closing, normally-closed, master valve icl' controlling the iiow ol working iiuid to the motor and pressure operated means lor opening it, a main working riuid supply line connected to salu master valve and normally closed thereby, a pair of manually operable control valves each lia ving an inlet poi-i.l an exhaust port, and an outiet poi t, said valves normally arranged with their inlet poi-ts closed and their outlet ports communieating to atmosphere through said exhaust ports and operable to open their inlet ports in communication with the outlet ports and to close their exhaust ports, a tank connected in the main line through a throttle valve arranged to time the now oi' huid from the main line to said tank and une building up of main line pressure in the tank, said tank being also connected in the main line through a normally closed replenishing valve operable, when open, to instantly replenish the valve in said tank and operatinli means lor opening it, the inlet port of each valve being connected to the tank and the outlet ports oi said valves being connected in multiple with the pressure operated means of the master valve and with tile operating means or said replenishing valve. the tank being or sumcient capacity to supply riuicl to the pressure operated means oi' the master valve suliiclent only for one opening operation oi the master valve, all whereby upon operating only one ol tiie control valves the working huid exhausts from the tank through trie other control valve leaving an insumclent supply oi said uuid to operate the pressure operated means ot the master valve upon subsequent operation oi said other control valve. and the operation oi both control valves substantially simultaneously is required to operate the master valve.

ERNEST DAVIS. 

